The present invention relates to a power converter for controlling electric power supplied to a load, and an electric power system and a mobile body equipped with the power converter.
In an electric power system for supplying electric power to a load, a power converter is controlled according to load current flowing through the load, thereby controlling electric power supplied to the load. To do so, the electric power system is equipped with a current detector for detecting the load current flowing through the load.
Conventionally, in an electric power system for supplying electric power to a load, such as a motor drive system for converting direct current (DC) power from a storage battery into alternating current (AC) power and supplying it to a motor which drives an electric car or hybrid car, a current detector, for example, which has been disclosed in Japanese Laid-open Patent Publication No. Hei 11-136960, is incorporated in a power converter for converting DC power into AC power so as to detect current supplied to a motor. This conventional current detector is created such that a Hall element is placed in the gap of the annular magnetic core that is fitted into a bus bar which functions as an output conductor of the power converter's circuit module. The aforementioned current detector is fitted into a cooling block which is a component of the power converter's circuit module.
Furthermore, as disclosed in Japanese Application Patent Laid-open Publication No. 2001-221815 and Japanese Application Patent Laid-open Publication No. 2002-40058, a current detector has been proposed in which a Hall element is disposed at the center inside the letter-U shaped conductor and magnetic flux concentrated in the area is directly inputted into the Hall element, thereby detecting current flowing through the letter-U shaped conductor. This current detector is created such that a first part consisting of a letter-U shaped conductor and a resin formed body, a support plate to which a semiconductor chip including a Hall element is fixed, and a second part consisting of a lead terminal and a resin formed body adhere to one other.
Furthermore, recently, as disclosed in Japanese Application Patent Laid-open Publication No. 2000-19199, a current detection method has been proposed in which a current path is formed symmetrically with respect to an axis or a point, and a Hall element is disposed at a location where magnetic flux density at a central portion of the current path is almost constant, thereby detecting current flowing through the current path inexpensively and by using a small device.
In an electric power system for supplying electric power to a load, such as a motor drive system for converting DC power from a storage battery into AC power and supplying it to a motor which drives an electric car or hybrid car, how to make a power converter for converting DC power into AC power small and inexpensive has been studied in order to inexpensively make electrically-operated vehicles such as electric cars and hybrid cars, increase fuel efficiency and travel distance per one battery charge, and reduce space for mounting the power converter.
To achieve the above objectives, it is desirable that among all components of the power converter, high-voltage components which require certain intervals to insulate one another and components which generate heat when a large current is applied be integrated and made compact thereby forming a module having excellent insulation and heat discharge performance. A variety of modules have recently been proposed. As disclosed in the aforementioned Japanese Laid-open Patent Publication No. Hei 11-136960, a module which incorporates a current detector has been proposed.
However, a current detector disclosed in Japanese Laid-open Patent Publication No. Hei 11-136960 requires a magnetic core. For that reason, it is impossible to dispose a current detector inside the cooling block without making the cooling block large. That is, in a current detector using a magnetic core, to detect current flowing through a current-carrying conductor, it is necessary to adjust the amount of magnetic flux by adjusting the gap width, to make the effective sectional area of the magnetic core large, and to make the effective length of the magnetic path short so as to prevent the magnetic core from becoming saturated. As a result, it is difficult to make the magnetic core small. Accordingly, when the magnetic core is installed inside the cooling block, the cooling block needs to be made large. Furthermore, when the magnetic core is installed on the side wall of the cooling block, it is necessary to make the side wall of the cooling block protrude outward to dispose the magnetic core. As a consequence, there is no other choice than to make the cooling block large.